1. Field of the Invention
The present invention relates to a gas laser blower which forcibly circulates a laser gas in a processing gas laser apparatus and the like.
2. Prior Art
Recent high-speed axial flow type carbonic acid gas laser apparatuses (a CO.sub.2 gas laser oscillation apparatuses) not only can provide a high output while it is compact but also can generate a high quality laser beam, so that they are becoming widely used for a laser processing such as cutting of metallic or non-metallic materials, welding of metallic materials and the like. Particularly, their applications are increasing rapidly in the field requiring a material to be cut to a complicated shape at a high speed and a high accuracy in the form of CNC laser processing machines which is connected to, a CNC computerized numerical control apparatuses.
In the carbonic acid gas laser apparatus, about 20 percent of electric energy inputted is converted into a laser beam and the remainder thereof is consumed in heating a laser gas. Theoretically, a laser oscillation gain is in proportion to -(3/2) power of an absolute temperature T. Accordingly, in order to raise the oscillation efficiency, it is necessary to forcibly cool the laser gas so as to lower the temperature of the laser gas as much as possible. Thus, in the case of a carbonic acid gas laser apparatus of a high-speed axial flow type, a turbo blower for a gas laser and the like are employed for forcing the laser gas into the cooling device by forced circulation of the laser gas within the apparatus.
An example of a conventional turbo blower for a gas laser is shown in FIG. 3. In FIG. 3, a turbo vane 1 of a turbo blower 100A for a gas laser is connected to an upper end of a shaft 2 by a nut 7. A rotor 3 is fixed to the shaft 2 along the outer periphery thereof by a shrinkage fit. A stator 4 is provided outside the rotor 3. The stator 4 is fixed to a housing 120 and constitutes a high frequency motor 30 with the rotor 3. The shaft 2 and the turbo vane connected thereto are rotated at a high speed of tens of thousands RPM by this high frequency motor 30.
An upper portion of the shaft 2, that is, a portion of shaft between an upper end of the rotor 3, constituting the high frequency motor 30, and an upper end of the turbo vane 1, which are respectively mounted on the shaft 2, is supported by a ball bearing 5 mounted on an upper portion of the housing 120, and a lower portion of the shaft 2 is supported by a ball bearing 6 mounted on a shaft supporting portion formed in a lower portion of the housing 120, respectively.
Oil in an oil reservoir 170 is supplied to the ball bearings 5 and 6 by a pump 16 which utilizes a centrifugal force to lubricate these ball bearings 5 and 6. Then, the oil supplied to the ball bearings 5 and 6 is returned to the oil reservoir 170 after passing through an oil passage 140 and an internal chamber of the housing 180. The oil is cooled by cooling water which flows in a cooling water passage 190 provided along the oil passage 140 when the oil passes through the oil passage 140. By this cooling, the oil gives off its heat absorbed while lubricating the ball bearings 5 and 6.
In this way, the oil is repetively heated and cooled as it circulates during operation of the turbo blower 100A for the gas laser, so that a large amount of oil and oil mist 160 exist within the housing 120.
In order to prevent the oil and oil mist 160 from passing the interior of the housing 120 to enter the carbonic acid gas laser apparatus, it is structured that a vacuum pump (not shown) discharges the laser gas from the internal chamber 180 of a housing through a vacuum discharge port 22 so as to always keep the pressure in the internal chamber 180 of housing lower than that within the turbo vane chamber.
In the above structure, the oil, particularly the oil which lubricated the upper bearing 5, scatters into mist while returning to the oil reservoir passing through the oil passage 140 and to the internal chamber 180 of housing, thereby floating in the internal chamber 180 of housing. Thus, when the gas within the internal chamber 180 of housing is discharged through the vacuum discharge port 22 by the vacuum pump, the floating oil mist is discharged together with the laser gas so that a considerable amount of oil is lost during a long period of time.